« 이전계속 »
creek, appeared to be principally composed of the washings of the escarpment, and was nearly level with a very slight dip towards the creek.
Dr. Dawson, who carefully examined the Missouri Coteau, thus speaks of it: “One hundred and twenty miles west of Turtle Mountain, the second prairie plateau comes to an end against the foot of the great belt of drift deposits, known as the Missouri Coteau.
“The Missouri Coteau is one of the most important features of the western plains, and is certainly the most remarkable monument of the glacial period now existing there. Though frequently mentioned in western reports, I cannot learn that its structure has yet been carefully studied. I have had the opportunity of examining more or less closely that portion of it which crosses the forty-ninth parallel, for a length of 100 miles.
“Where cut somewhat obliquely by this parallel, the Coteau may be said to extend for a distance of forty-five miles. At right angles to its general course, however, its extreme width at this point cannot be more than thirty miles. On approaching it from the east, on the trail from Wood End, which, as already stated, is somewhat more elevated than the prairie lying east of it, a gradual ascent is made, till the edge of the Coteau is reached, amounting in a distance of twentyfive miles to about 150 feet. The country at the same time becomes more distinctly undulating—as on approaching Turtle Mountain from the east—till, almost before one is aware of the change, the road is winding among a confusion of abruptly rounded and tumultuous hills, which consist entirely of drift material, and in many cases seem to be formed almost altogether of boulders and gravel, the finer matter having been to a great extent washed down into the hollows. Where it appears, however, it is not unlike that of the drift of the lower prairies, being yellowish and sandy. Among the hills are basin-like valleys, round, or irregular in form,
and without outlet, which are sometimes dry but generally hold swamps or small lakes, which have frequently been filled in with material washed from the hills so as to become flatbottomed. The hills and valleys have in general no very determinate direction, but a slight tendency to arrangement in north and south lines was observable in some parts of this region. The hills culminate on the line about the 305th mile point, and westward from this point they are neither so steep nor so stony. The country gradually subsides from its rough and broken character, to that of rather boldly undulating prairie, without, however, falling much in general elevation below the tops of the bolder hills further east. We have, in fact, passed up over the margin of the third great prairie steppe.
“ The whole of the Coteau belt is characterized by the absence of drainage valleys, and in consequence its pools and lakes are very often charged with salts, of which those most abundantly represented are sodic and magnesic sulphates. The saline lakes very generally dry up completely toward the end of the summer, and present wide expanses of white efflorescent crystals, which contrast in color with the crimson Salicornea with which they are often fringed. The crystalline crust generally rests on a thick stratum of soft black mud.
The boulders and gravel of the Coteau were here observed to be chiefly of Laurentian origin, with, however, a good deal of the usual white limestone, and a slight admixture of quartzite drift. On the western margin some rather large disused stream valleys were seen, holding chains of saline lakes; but their relation to the drift materials of the Coteau were not so clearly shown as in other localities further north, to be described.
“In passing westward, from the last exposures of the tertiary rocks near Wood End, to the locality of their first appearance within the Coteau, a distance of about seventy
miles, we rise about 600 feet and attain an elevation of about 2,500 feet above the sea. The slope of the surface of the Lignite Tertiary then, assuming it to be uniform, is a little less than one hundred feet per mile; and on and against this gently inclined plane, the immense drift deposits of the Coteau hills are piled.
“Passing westward for about seventy miles, it is found to preserve much the same appearance. The prairie of the Coteau foot is rather undulating, and slightly raised above the general level, but the edge of the hilly country of the Coteau itself, is always from a distance well defined. To the northward and eastward, boundless level, treeless plains stretch to the horizon. The Traders' Road to Wood Mountain, after passing along the base of the Coteau for the distance above indicated, turns westward and crosses it, taking advantage of a deep bay in its edge, in which also rises a main tributary of the Souris River. The road then passes for about fifty miles through the Coteau belt, which must here be about thirty miles wide, and repeats almost exactly the physical features already described, though in this particular locality neither quite so tumultuous nor so stony as on the line.
“Following the Traders' Road westward for about twentyfive miles toward Wood Mountain, it passes for the most part between the southern edge of the Coteau proper, and the northern margin of the Tertiary plateau. Wherever from any hill, a view over the Coteau to the north can be obtained, it is seen to stretch away to the horizon in a succession of wave-like mounds and ridges, which do not differ much in average altitude.
“The intervening region, followed by the road on account of its facility, has characters of its own. Wide and deep valleys, often flat-bottomed, with systems of tributary coulées are found everywhere cut in the soft rocks of the foot of the Tertiary plateau. Some have small streams still flowing in them, fed by the drainage of the plateau; but for the most part these old valleys are dry or occupied by chains of small saline lakes, the waters of many of which disappear early in the summer. The lakes usually have the long river-like forms of the valleys which contain them, and receive the waters of the brooks which still flow. One of the most important, probably nine miles in length, forms the drainage basin for the streams of Wood Mountain ; its sides are abrupt and the water appears to be deep. These old valleys are evidently of pre-glacial age, and have formed a part of the original sculpture of the country. The heaping up of the great drift deposits of the Coteau along the foot of the Tertiary plateau, has blocked them up, and prevented the drainage finding its way northward as before. Since the elevation succeeding the glacial subsidence, the rainfall of the dis trict has never been sufficiently great, in proportion to the evaporation, to enable the streams to cut through the barrier thus formed. The existence of these valleys, and the arrangements of the drift deposits in this region, have important bearings on several problems connected with its general history.”
The Coteau resembles Turtle Mountain in its physical features and like that district would no doubt be thickly wooded but for the prairie fires, which have sometimes run hundreds of miles in the dry weather of autumn. As it is, the want of wood is one of the most serious drawbacks, and animals fed over these hills in summer would require to be wintered in some of the river valleys to the north, or in the wooded ravines of the Tertiary plateau to the south. The plateau of the Lignite Tertiary is for the most part adapted for pastoral purposes, and being covered with a good growth of grass, is well suited for this use. The strip of country between the plateau and the southern edge of the Coteau, partakes in some measure of its character, but has a less favorable appearance.
One important advantage of this plateau is the exis along its edges of sheltered ravines and valleys, conta groves of poplars. Another is the presence beneath it o deposits of lignite coal. In one of these sheltered va the Half-breed settlement known as Wood Mountai situated. Here there has been stationed for a numb years a large detachment of the Mounted Police, and her Sitting Bull made his headquarters after the slaughter og American soldiers under Custer. In past time Wood M tain was a noted locality, as the buffalo roamed in coun thousands u 'er the wide prairies on every hand, and hunters had only to kill and eat, as game abounded. this is changed, and now buffalo are becoming so scarce in the vicinity of Wood Mountain they scarcely appear.